P0690Generic code

P0690 Code: ECM/PCM Power Relay Sense Circuit High

The P0690 code means the control circuit of the engine computer power relay shows high voltage, which points to an open circuit or a short to voltage. It can cause a no start or an engine that shuts off while driving. Check the fuse, relay, connector and wiring before replacing any part.

Severity
High
Can I keep driving?
Yes, but with caution
Estimated cost
$15 to $300
Difficulty
Medium
System
Computer and Outputs
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the P0690 code means

On many vehicles the engine computer gets its power through a main relay that the computer itself controls. It switches the relay on when you turn the key to run and keeps it on for a few seconds after you shut the engine off so the computer can save its data.

The computer watches the control circuit from its own driver transistor. The P0690 code tells you the voltage in that control circuit is high, which means an open circuit or a short to voltage. Before you replace any part, check the fuse, the relay, the connector and the wiring, because those are the most common causes.

If the relay fails, the computer can lose power while you are driving (the engine shuts off) or it may not be able to save its data when you switch the car off. A relay that sticks closed keeps the computer powered up and drains the battery.

To confirm the fault, measure the continuity of each wire between the relay connector and the computer connector with the key off. It should be under 1 ohm, and an infinite reading means the wire is open. If the wiring checks out, measure the relay coil itself: an infinite resistance confirms it is open inside.

P0690 code symptoms

  • Check engine light or another warning light on.
  • Engine will not start or shuts off.
  • Engine suddenly dies or will not crank at all.
  • Dead battery after the car sits for several days.

Likely causes of the P0690 code

  1. Loose or broken connector. The most frequent cause, especially after another repair.
  2. Open relay coil or motor. The resistance reads infinite.
  3. Cut control wire between the relay and the computer.
  4. Short to 12 volts. The control wire touches another wire that carries voltage.

How to diagnose the P0690 code step by step

  1. Command the relay with the scan tool and check whether it responds.
  2. Check the fuse and the relay. Measure voltage on both sides of the fuse, and swap the relay with an identical one.
  3. Measure the supply at the connector. You should see battery voltage with the key on or when the relay is commanded.
  4. Measure the relay resistance and compare it with the manual. Also check the insulation to ground.
  5. Check the control wire for continuity all the way to the computer and for any short circuits.
  6. Swap in an identical relay to rule out the original one.
  7. Check that the relay turns off after shutdown, which should happen within a few seconds or minutes.

How to fix the P0690 code

  • Repair the connector, the wiring or the power supply.
  • Replace the PCM power relay if it does not respond when it has correct power and a correct control signal.
  • Clear the P0690 code and verify the repair with a test drive.

Technical reference data

  • 12 volt relay in the engine compartment fuse box.
  • Reference values only: check the manufacturer data for your vehicle.

Brand-specific notes

The source reports this code as frequent on Mazda, Ford and Volkswagen vehicles. The same fuse, relay, connector and wiring checks apply on all of them.

P0690 on Mazda

Frequent on Mazda. Start with the fuse and relay before replacing anything else.

P0690 on Ford

Frequent on Ford. Check the connector and the control wiring before you buy a part.

P0690 on Volkswagen

Frequent on Volkswagen. Test the relay and its supply first, since they are the most common causes.

Frequently asked questions about P0690

What does the P0690 code mean?
It means the control circuit of the engine computer power relay has high voltage. The cause is an open circuit or a short to voltage.
Can I drive with a P0690 code?
Only with caution. The engine can shut off without warning or fail to start, which is a safety risk in traffic, so get it checked soon.
What does the PCM power relay do?
On many vehicles the computer is powered through a main relay that it controls itself. It switches the relay on with the key and keeps it on for a few seconds after shutdown so it can save its data.
Do I always have to replace the part?
No. Check the fuses, relays, connectors and wiring first, because they cause most of these codes and cost very little to fix.
How much does it cost to fix P0690?
As a rough guide, between $15 and $300, depending on whether it is a fuse, a relay or a wiring repair.

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